AutoDesk 123D Make
123D Make is slicing software often used in conjunction with a laser cutter or CNC router instead of a 3d printer. This program allows you to slice a digital 3d model into layers of any thickness you choose, with the intent of then stacking those layers in order to create a large 3d model out of materials such as cardboard or plywood. It can also be used to create complicated 3d models which can be assembled like puzzles.
123D Make is free software provided through the AutoDesk 123D collection, anyone can download and install it for free on their personal computer.
UPDATE 3/21 123D Make will cease to exist on March 31st, 2017. However, the program can still be accessed through the link below. Note that this software is no longer supported by AutoDesk.
Install Link: Install 123D Make